This invention relates to optical switch arrays comprising a plurality of optical switches of the kind utilising the interaction between light propagating along one of two waveguide path sections in close proximity to one another and an electrical field produced by electric switching voltages applied between electrodes actively associated with the waveguide path sections in order to effect switching of the light from one of the waveguide path sections to the other.
The waveguide path sections of the switches may, for example, comprise sections of waveguide channels or stripes of titanium diffused into the surface of a lithium niobate substrate in close proximity to one another with a pair of electrodes being formed on the surface of the substrate closely adjacent to the diffused waveguide channels with the interposition of insulating material between the electrodes and the substrate surface. The optical switches may, alternatively, comprise a substrate of gallium arsenide, indium phosphide or other III-V material in which a so-called Schotkky layer is provided between electrodes and the substrate instead of waveguide channels being diffused into the substrate.
Whatever the particular form of optical switch is employed the flux lines of the electric field cut through the closely adjacent waveguide path sections in order to effect switching of light from one waveguide path section to another.
For the purpose of providing an array of such optical switches to facilitate complex optical switch routing arrangements it has hitherto been the practice to form the switches of the optical array on the same substrate but to electrically isolate the respective switches from one another by sufficient spatial separation between switches. Due to space considerations this technique has necessitated the provision of relatively sharp bends in waveguide sections linking the closely adjacent waveguide path sections of the optical switches. These waveguide section bends are lossy and occupy valuable substrate space. Another known technique for providing the requisite optical switch isolation resides in the provision of extremely narrow milled slots in the optical array substrate at positions between those waveguide sections which link the switches and which need to be electrically isolated from one another. However, the milling of such slots needs to be formed with precision and renders this technique unduly costly and time comsuming especially in volume production of optical switch arrays.